A man admitted yesterday he fatally stabbed his ex-lover and her young daughter, and wounded her husband and another daughter.

In a plea deal in Queens Supreme Court, Moo Chul Shin said he went on his blood spree after his paramour failed to follow through on a promise to commit suicide with him if they couldn’t be together.

While they were estranged from their spouses, Shin, 31, said he and Sook Kim, 34, agreed to take their own lives if they ever broke up.

But Shin said that despite their death pact, Kim left him and returned to her husband, leaving Shin to recover from a failed suicide bid.

“They should die together rather than be separated,” lawyer Jin Han said after his client pleaded guilty to first- and second-degree murder and attempted murder in the Jan. 3 rampage.

Han said Shin and Kim both divorced their spouses and were living together in Virginia. When she decided to reconcile with her spouse in December, “there was a lot of emotional turmoil.”

Kim accompanied Shin to the store when he “purchased an extraordinary amount of drugs” and later “ingested a large number of drugs,” Han said.

Shin was rushed to the hospital and fell into a coma. While he lay in the hospital for 11 days, Kim took nearly $4,000 from their joint account, sold his furniture and moved back with her husband in Woodside, Queens, Han said.

That’s when Shin drove to New York with a blood lust, he admitted in court.

“I came to New York from Virginia. I stabbed the husband first,” Shin told Supreme Court Justice Robert Hanophy through a Korean translator. “I went to my girlfriend’s house and stabbed her. I stabbed the little children also.”

When the dust settled from the brutal knifings, Sook Kim and her 7-year-old daughter, Clara, were dead and Kim’s husband Hyun Kim, 38, and daughter Estell, 8, were left fighting for their lives. Shin went to a motel and slit his wrists, but was found in time.

As part of the plea agreement, Shin will get 39 years to life. Han told Hanophy his client, who could have faced the death penalty for the murders, agreed to plead guilty because “he doesn’t want to put his family and the victims’ family through the hardship of a trial.